Terrestrial Cr-spinels in the Maiolica limestone: Where are they from?
Davide Lenaz, Birger Schmitz, Walter Alvarez, "Terrestrial Cr-spinels in the Maiolica limestone: Where are they from?", 250 Million Years of Earth History in Central Italy: Celebrating 25 Years of the Geological Observatory of Coldigioco, Christian Koeberl, David M. Bice
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In total, 33 and 65 chrome-spinel (Cr-spinel) grains in the >63 and 32–63 µm size fractions, respectively, were recovered from 12 beds in two stratigraphically separated groups along the 240-m-thick Monte Acuto section of the Maiolica limestone in central Italy, spanning from the Berriasian to the early Hauterivian. The chemistry of these detrital spinels suggests they may represent windblown ophiolitic detritus, showing the evolution of an ophiolite evolving from a mid-ocean-ridge basalt setting (Bosso section) to a suprasubduction-zone setting, including a backarc and an arc setting (Monte Acuto section). The source of the Maiolica detrital minerals may have been the obducting ophiolites of the Albanides and/or the Hellenides, which show a similar evolution. In this case, it is particularly important to note how the Cr-spinel detritus in the Maiolica limestone records this evolution over a relatively short period of time, lasting ~10 m.y.
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250 Million Years of Earth History in Central Italy: Celebrating 25 Years of the Geological Observatory of Coldigioco
Central Italy has been a cradle of geology for centuries. For more than 100 years, studies at the Umbria and Marche Apennines have led to new ideas and a better understanding of the past, such as the Cretaceous–Paleogene (K-Pg) boundary event, or the events across the Eocene–Oligocene transition from a greenhouse to an icehouse world. The Umbria-Marche Apennines are entirely made of marine sedimentary rocks, representing a continuous record of the geotectonic evolution of an epeiric sea from the Early Triassic to the Pleistocene. The book includes reviews and original research works accomplished with the support of the Geological Observatory of Coldigioco, an independent research and educational center, which was founded in an abandoned medieval hamlet near Apiro in 1992.